The present invention relates to a ball-type control device, for controlling the movements of a cursor on a screen of an electronic apparatus. The control device includes an actuation member in the form of a spherical ball that has a convex spherical surface, called the detection surface, that is capable of being manipulated by a user. The control device is commonly called a “trackball” in which the surface of the ball is manipulated directly by the fingers or the hand of the user.
The invention relates to a control device of the “optical” or optoelectronic type comprising a ball casing that has a concave face that surrounds at least a portion of the ball. The control device has a casing with at least one window for light beams to pass through for detecting the rotation of the ball, and has elements for rotational guidance of the ball, such as rolling spheroids that protrude through the concave face of the casing and on which the ball, when it is manipulated, rolls in order to rotate about its center. The control device also has a light source to emit at least one incident detection light beam towards the ball, and finally means, comprising particularly a lens and means forming image sensors that receive light originating from the zone of the ball lit by the incident detection light beam.
Such a general design is known from document DE-A-3.407.131 published in 1985 that describes a mouse whose ball is mounted so as to rotate in a ball casing, or shell, in which it is guided in rotation by spheroids each of which is itself received in a matching cavity on the concave surface of the shell that houses the ball. Such device comprises two sets of light-emitting diodes and optical sensors that form the optical means for detecting any rotary movement of the ball about its centre in order to convert these rotary movements into electronic signals.
Accordingly, the convex spherical surface of the ball comprises an even and evenly distributed pattern over the whole surface of the ball that is lit and whose image is captured, through a lens, by the sensors then analysed by known image processing means.
Such a design is particularly advantageous because, with a particularly small number of components, it makes it possible to detect and analyse the rotary movements of the ball without elements in contact with the ball, the only moving mechanical component consisting of the ball itself.
The casing of the device, in this instance of the mouse, also comprises, on the outside, keys for actuating various switches that can be actuated by the fingers of the user who is manipulating the mouse, for example for transmitting signals, for example for validating a position of a cursor on a computer screen.
Many examples are known of transposing the teachings of this document for the design of a trackball in which a top portion of the ball protrudes from the casing to allow it to be manipulated directly by the user's hand.
Such a control device or trackball may be used in many applications, particularly when it has very small dimensions in a portable electronic apparatus such as a telephone called a portable or GSM telephone, or else in a personal digital assistant (PDA).
When it has larger dimensions, a trackball may also be used, for example, on board a motor vehicle, in the passenger compartment of the vehicle, to control various functions via a display screen on which a cursor moves.
The invention aims to propose an enhancement of such a ball-based control device.